Marine fish larval rearing (e.g., gilthead seabream Sparus aurata and seabass Dicentrarchus labrax), is the most critical developmental phase, characterized by high and unpredictable mortality rates. In recent years, significant progress has been made in zootechnics, nutrition, and welfare, with standardization of cultivation conditions, introduction of new ingredients and feed supplements, and development of various analytical tools (e.g., hematological parameters, enzymatic activity measurements and gene expression profiling).
This work describes the methodologies implemented at EPPO/S2AQUAcoLAB for conducting trials with fish larvae and juveniles to evaluate new diets and supplements (e.g., functional ingredients) or cultivation techniques (e.g., fish density, photoperiod, water temperature, oxygen levels, etc). Performance data, including weight, length, and survival is collected during each trial. Analytical procedures are carried out in the laboratory to study fish physiological parameters (e.g. oxidative stress, gene expression, fatty acids profile, proximal composition, immunological and other welfare parameters). Additionally, challenge tests involving bacterial infection (via bath or injection) or stress events (e.g. air exposure, crowding, swimming resistance, hypoxia) can be conducted to assess fish resistance or susceptibility, by assessing mortality over time. Whole larvae or juvenile organs can also be sampled to evaluate fish resistance (fig. 1).
Acknowledgments: The present work was financed by the projects INOVAQUA (MAR-021.1.3-FEAMPA-00004; ALGAFEEDS PACTO DE INOVAÇÃO BIOECONOMIA AZUL (Project No. C644915664-00000026) and SAUDE & AQUA II (MAR-021.1.3-FEAMPA-00018).